One of my favorite sayings is that thinking is work and people are lazy. It's right up there with wondering why common sense is so uncommon, and with distrusting anything written by journalists. Needless to say, I have once again been disgusted with a matter badly misrepresented in the press. This opinion piece is about a claim that the SL-1 reactor accident was the first nuclear accident in the USA.

Introduction: The SL-1 Reactor

My brother borrowed and recently returned to me one of the most readable books ever written about a reactor accident: _Idaho Falls_ by William McKeown. It's a decent read and I recommend it. The book is a good account of the only fatal nuclear power plant accident to ever occur in the United States. The reactor involved was a US Army prototype called the SL-1, built and operated on the grounds of the National Reactor Testing Station (NRTS), which has since been rebranded as the Idaho National Lab (INL). I used to work there.

The SL-1 was a US Army project. In the 50s and 60s, the Army was responsible for radar stations north of the Arctic Circle. These installations were built to monitor any incursions into American and Canadian airspace by Soviet bombers. Most of the radar locations were far from the electric power grids of North America. As a consequence, the Army was exploring the concept of small nuclear reactors simple enough that a small crew could run them and small enough that all the components could be built elsewhere and airlifted in. The Army investigated a handful of small reactor designs and prototyped at least two: the SL-1 and the ML-1, both built and operated at the NRTS. This is not as stupid as you might think. You would never guess this from reading about power generation in the news media, which is where most people get their info, but nuclear power is not that expensive on a cost per kilowatt-hour basis compared to other methods (there are many sources for this sort of info; a good place to start is at Even when regulatory burdens are figured into the equation, nuclear power is in the middle of the pack for electricity production costs, with solar and wind power being much more expensive. Don't take my word for this. Go look at the analyses by the Dept. of Energy and other groups with your own eyes and your own brain - and make your own evaluation.

During the time when the Army was exploring reactors for remote radar stations, they were aware of the costs. The SL-1 design was essentially a disposable reactor. The reactor core was good for about 5 years without refueling; however, the reactor was not designed to be refueled insitu. At the end of its life, the core would be removed and replaced by a whole new core delivered by airlift. The operators of an SL-1 would never do their own refueling, greatly simplifying the reactor's operation and reducing the number of staff required. The concept of using a reactor rather than a fossil fuel-driven generator had huge appeal since it would eliminate the significant expense of constantly delivering diesel or fuel oil to remote locations where lousy weather was the norm. The US Navy was transitioning to an entirely-nuclear powered submarine force for the same reason: the elimination of the constant need to refuel.

I reread _Idaho Falls_ last week while tidying up. That's a bad habit I have, the propensity to be ambushed by something good to read. I do have some caveats about McKeown's narrative though. My first exposure to the SL-1 reactor accident was through the original reports published by the Atomic Energy Commission (AEC). In fact anyone can read these for themselves even though it's a bit of a slog through rather dry engineer-speak and the AEC's bad habit of non-overlapping sequential reporting. Having read all of the available AEC reports for myself, I know that there are spots where McKeown glossed over details and left out some stuff I think he ought to have left in - like the ultimate fate of the ambulance. What McKeown did and did not cover was quite the topic of conversation at the INL when the book came out. To get an idea of where McKeown was a little too glib I would point the interested reader toward the reviews on where several folks actually present at the SL-1 accident and investigation had a few things to say. Regardless, where McKeown's text really shines is in telling the story of the SL-1 from the human interest perspective despite its small number of flaws.

America's First Nuclear Accident?

Right off the bat, let me make it clear that we're talking about accidents, injuries and deaths where the primary cause is ionizing radiation. This is a very specific category. Not only do we exclude more prosaic accidents like falls and electrical fires and mechanical machinery failure, we also exclude here accidents or illnesses from passive non-ionizing radiation. There's a huge radiation source we live with everyday and that's the sun. On the ground under our protective atmosphere, the sunlight that reaches us is passive radiation. By the time it arrives at the surface of the earth, the constant rain of solar particles give us both heat and light - but to a first order approximation, none of it is ionizing. Ionizing radiation by definition creates new ions or particles (spontaneous fission of U232) and changes ion energy states resulting in energy emissions (e.g., passive gamma radiation of K40). X-rays are ionizing, as are gamma rays, beta radiation (emitted electrons), alpha radiation (emitted positively-charged helium ions) and the neutron flux inside a nuclear pile.

The one thing that has always annoyed me about McKeown's book is the subtitle on the front cover: "the untold story of America's first nuclear accident." That subtitle is repeated on the book's page. That claim shows up on search results headers in big type you do a google search on "idaho falls sl-1 book." That's quite a claim and one for which McKeown never actually presents evidence. In fact, one of the reasons I picked the book up in the bookstore was that subtitle - because I knew it was not true. I'm a real sucker for targeting demonstrable errors.

The SL-1 accident happened in 1961 during the reactor's third year of operation. It was not a meltdown sensu stricto leading to the creation of corium - though some of the fuel did melt, it did not stay in the molten state. The SL-1 suffered what is known as a prompt criticality accident. During maintenance, one of the control rods was removed too far out of the reactor core, allowing a brief chain reaction to occur. The heat from this unwanted nuclear excursion flashed some of the cooling water to steam. The steam acted as a hydraulic hammer which blasted control rods and fuel assemblies out the top of the reactor vessel. The force of the steam-driven hydraulic hammer also lifted the reactor vessel itself upward nine feet in the air before it dropped back down. The super-heated steam explosion killed or fatally injured the three reactor operators who were working on or next to the reactor vessel cap. A great deal of radiation was emitted; and if the operators had not already been fatally injured or killed by the explosion, they would have been dead from radiation poisoning within a day. Despite the high levels of radiation inside the reactor building, that building acted like a containment structure and kept most of the radioactivity inside. The deliberate destruction of the Borax-1 reactor in a prompt criticality experiment at the NRTS in 1954 was larger event and much messier, releasing radioactive contamination over a 2 acre area ( Like the excursion that destroyed the SL-1, the Borax-1 excursion caused a lot of its fuel to melt; however, none of the melted fuel stayed melted, so this too was not a true corium-producing meltdown. Just because fuel melts in an exursion doesn't mean it's a real China-syndrome meltdown.

There is a great deal of info available on the SL-1 event, including McKeown's book, a very readable overview narrative from the DOE (, and a wikipedia page that repeats some of mistakes the McKeown made in his book. If you're okay with engineer-speak, the original accident report for the AEC is online at the INL at: For what it's worth, you can watch the destruction of the Borax-1 reactor at

Getting back to our main topic, it is apropos to inquire what McKeown meant by "America's first nuclear accident"? There's a lot of ground to cover here. Did he mean the first fatal accident from handling fissionable radioisotopes? I know of at least two fatal ones from Los Alamos in 1945 and 1946. Howabout the first accidental reactor fuel melting? Nope - that's probably the EBR-1 in 1955, Fermi's pet breeder reactor project at the NRTS and the first reactor to turn a generator to make electricity. The EBR-1 is now a national landmark and is open as a museum from Memorial Day to Labor Day. Howabout the first documentable deaths from handling radionuclides? Nope, I think that's probably Madame Curie herself. The first occupational injuries and/or deaths from exposure to radionuclides on the job? I believe that honor may go to the women who died from licking their brushes used for radium paint. This activity had a peak during World War I since the military desired and could afford instrument gauges that could be read in the dark. The war was followed by the now well-documented jaw cancer cluster in New Jersey in the 1920s.

The bottom line here is that the SL-1 accident was not America's first nuclear accident. The only thing the SL-1 accident can claim is the dubious honor of the world's first fatalities while operating a nuclear power generation station, i.e. while operating a reactor designed and used for the generation of electricity. To my knowledge, the three deaths at the SL-1 were the first and remain the only fatalities sustained while operating a nuclear power generation station in North America. These deaths were the only nuclear power plant fatalities due to radiation in the world up until the accident at Chernobyl. The label of America's first nuclear accident is incorrect. Given that the details of nuclear accidents are abundantly documented and available publicly, I find it unlikely that McKeown was ignorant of these. I am forced to conclude that either McKeown or his publisher used the "first nuclear accident" description on the cover of the book for marketing purposes, assuming that most people were ignorant enough to believe the lie.

Note: Just to preemptively head off any commentary about nuclear fatalities on Soviet submarines, the first known fatalities were aboard the K-19, the so-called "Widow Maker" and the inspiration for the Harrison Ford movie of the same name occurred in July 1961 ( So even if we compare the SL-1 power-generation reactor accident with the K-19 ship-propulsion reactor accident, the SL-1 still retains its dubious status for the first known power-generation reactor fatalities.